From U.S. Pat. No. 3,995,617 a heart assist catheter pump is known which includes a catheter having a distal end for insertion from the aorta past the aortic valve into the left ventricle. The distal end has inlet openings and a check valve for allowing inward flow. Spaced from the distal end, the catheter has outlet openings and a set of second check valves for allowing outward flow. A pump device communicating with the proximal end of the catheter alternatingly generates a suction causing blood to be withdrawn from the left ventricle into the catheter and to the pump device and an excess pressure causing blood to be reintroduced via the set of second check valves into the heart on the downstream side of the aortic valve. The second check valves are each formed by an elastic booth at the outside of the catheter.
Other examples of such a catheter pump for assisting the heart are known from U.S. Pat. Nos. 4,014,317 and 6,007,479.
During open heart surgery on an inactive heart, in practice blood circulation is usually maintained using a heart lung machine including a pump and an oxygenator. The pump is usually a non-pulsatile pump, which provides advantages in terms of design and compatibility with the function of the oxygenator (Allen et al.; “The importance of Pulsatile and Nonpulsatile Flow in the Design of Blood Pumps”; Artificial Organs 21(8): 922–928).
On the other hand, organ failure after open-heart surgery is a frequent cause of complications. Different theories regarding the causes of such organ failure exist. One of these theories is, that the use of a heart-lung machine has several side effects that may influence blood pressure and organ perfusion. For example, the heart-lung machine indices (a) a non-physiological (non-pulsatile) flow pattern, (b) a decreased blood viscosity when the priming liquid from the tubing and the oxygenator is introduced into the patient's blood circulation, (c) unwanted blood-material interactions. Reduced blood pressure can lead to reduced abdominal organ perfusion, which in turn can cause reduced organ functions. Other instances when reduced blood pressure may disturb organ functions are: during toxic shock, which may for instance be caused by an allergic reaction and, prolonged cardiac malfunction, which frequently entails multi-organ failure.
Several research results indicate that a pulsatile flow is advantageous for obtaining sufficient blood flow to the organs. For instance, pulsatile flow in a cardio pulmonary bypass has been found to have a positive effect on the blood flow rate to the kidneys of neonate pigs (Lodge et al.; “Regional Blood Flow During Pulsatile Cardiopulmonary Bypass and After Circulatory Arrest in an Infant Model”; Ann Thorac Surg 1997; 63:1243–50).
During an acute heart attack of a pig, blood flow to the liver and to the kidneys and microcirculation at cellular level were found to be improved if during three hour biventricular cardiac assist, the flow was pulsatile (Sezai et al.; “Major Organ Function Under Mechanical Support: Comparative Studies of Pulsatile and Nonpulsatile Circulation”; Artificial Organs 1999; 23(3): 280–285). During left ventricle cardiac assist in a similar situation, pulsatile cardiac assist provided superior circulation in the liver and superior microcirculation on a cellular level, at least in the initial phase of the treatment after the heart attack.
During open-heart surgery on neonate pigs, a positive effect of pulsatile flow on the blood flow to the organs, the brain and the heart muscles was found (Ündar et al.; “Effects of Perfusion Mode on Regional and Global Organ Blood Flow in a Neonatal Piglet Model”; Ann Thorac Surg; 68: 1336–43).
In clinical Cardiopulmonary Bypass cases, the results of measurement of cytokine, endothelium and other metabolic parameters indicated that the damage to the endothelium was less and the cytokine activation was reduced in a patient group treated with a pulsatile flow compared with another group treated with a non pulsatile flow (Orime Y. et al., “Cytokine and Endothelial Damage in Pulsatile and Nonpulsatile Cardiopulmonary Bypass”; Artificial Organs 1999; 23(6):508–512).